A little red-eyed frog could hold the key to ending the scourge of AIDS.
Scientists have found that a chemical in the skin of the Australian red-eyed tree frog can block infection by HIV - the virus that causes AIDS - by destroying the viral particles.
They hope further research could lead to an 'after-exposure' lotion to protect against HIV and AIDS.
Have your say » The chemical is part of the 21/ 2in-long frog's defences. Special glands on their skin produce and store packets of the compound, which is released when they are injured or alarmed and acts to protect them from infection by killing fungi, bacteria and viruses.
The ability to target HIV was discovered when researchers at Vanderbilt University in Nashville, Tennessee, decided to investigate whether the chemical was effective against viruses that infect humans.
In tests using human immune system cells, the chemical killed HIV particles but left the immune cells unharmed. It is thought to work by damaging the membrane of each viral particle, either by punching holes which cause it to fall apart, or through a 'detergent effect' which
breaks apart fatty molecules in the membrane.
Research leader Dr Scott Van-Compernolle said: 'There are lots of substances which destroy viruses but the trick is finding one that doesn't also destroy the membrane of our cells. That is why these frog peptides are unique.'
Further tests showed the chemical could stop the virus being passed between cells, thus blocking
infection. The scientists infected cells with HIV, treated them with the frog chemical and then exposed them to healthy cells. The virus appeared to have vanished.
They hope it will be possible to develop a cream to target infected cells. Dr VanCompernolle said: 'It seems it would work really well in just the way the frogs use it - as a cream. We envisage something prophylactic so if you were exposed to
HIV through unprotected sex, you could use this cream or a suppository to give you a fairly high dose of the proteins in the region where you thought the virus might be.'
It could still be effective if used hours after exposure. 'We showed you can successfully treat the infected cells up to eight hours after they were exposed to the virus,' said Dr VanCompernolle. 'The virus has already got in those cells but this is still able to block the infection.' The scientists have now won a grant from the American Foundation for AIDS Research to continue the work. Its director of research, Dr Rowena Johnston, said no creams exist which could be applied to the body after exposure to HIV.
But she added: 'The first generation of these products is now not far from being developed. They could be applied prior to sex or perhaps taken in the same way as the contraceptive pill.
'Alternatively, if the woman is HIV positive, she could protect her partner from infection. It would be a fantastic tool for HIV prevention. We are so far from having an AIDS vaccine, we are not going to wait around for 15 years and do nothing in the meantime.'
But destruction of the rainforest in north Queensland, Australia, means there are declining numbers of red-eyed tree frogs, which have bright green backs, yellow sides, a cream belly and orange inside legs.
Dr VanCompernolle said: 'These frogs have evolved over millions of years to produce these peptides. They have already tested them for us, to fight their own viruses and bacteria. Around the world there are huge and rapid declines in the numbers of amphibian species. When we don't take care of the ecosystems we have on the planet we risk losing something like this.'
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